You might be tempted to use image processing tools such as Photoshop or The GIMP when applying special effects to your user interface, but you'd be selling Java 2D's image processing tools short, as explained by Chet Haase and Romain Guy.

This chapter is from the book

IMAGE-PROCESSING tools such as Adobe Photoshop and The GIMP offer a wide variety of filters you can apply on your pictures to create various special effects (see Figure 8-1). When you are designing a user interface, it is very tempting to use those effects. For instance, you could use a filter to blur an out-of-focus element in the UI. You could also increase the brightness of an image as the user moves the mouse over a component.

Image Filters

Despite the impressive-looking results, image processing is not a difficult task to implement. Processing an image, or applying a filter, is just a matter of calculating a new color for each pixel of a source image. The information required to compute the new pixels varies greatly from one filter to another. Some filters, a grayscale filter for instance, need only the current color of a pixel; other filters, such as a sharpening filter, may also need the color of the surrounding pixels; still other filters, such as a rotation filter, may need additional parameters.

Since the introduction of Java 2D in J2SE 1.2, Java programmers have access to a straightforward image-processing model. You might have learned or read about the old producer-consumer model of Java 1.1. If you did, forget everything you know about it because the new model is much easier and more versatile. Java 2D's image-processing model revolves around the java.awt.image.BufferedImage class and the java.awt.image.BufferedImageOp interface.

A BufferedImageOp implementation takes a BufferedImage as input, called the source, and outputs another BufferedImage, called the destination, which is altered according to specific rules. Figure 8-2 shows how a blur filter produces the final image.

While the JDK does not offer concrete image filters, it does provide the foundations for you to create your own. If you need a sharpening or blurring filter, for example, you must know how to provide parameters to a ConvolveOp filter. We teach you such techniques in this chapter. Before we delve further into image-processing theory, let's see how we can use a BufferedImageOp to process an image.